Blood air trap chamber

ABSTRACT

A blood chamber for hemodialysis sets which comprises a sealed, flattened plastic parison, typically from blow molding, which defines a reservoir chamber and at least a first conduit communicating with a first end of the reservoir chamber through a first port. The conduit extends laterally along substantially the length of the reservoir chamber in spaced relation thereto, for connection with hemodialysis set tubing adjacent the reservoir chamber and opposed to the first end. The blood chamber typically also defines a second port communicating with the reservoir chamber, typically at the same end thereof as the first port.

This is a divisional application of Ser. No. 08/254,428 filed Jun. 6,1994 application allowed which inturn is a continuation of Ser. No.07/876,039 filed Apr. 30, 1992 which is now abandoned.

BACKGROUND OF THE INVENTION

At the present time, hemodialysis or plasmapheresis blood chambers, socalled air-trap blood chambers or "drip chambers" are typically madefrom two injection molded parts, comprising a round top cap which issolvent bonded to cylindrical chamber. Flow typically proceeds from ablood tube access port in the top cap out through an exit port at thebottom of the chamber. This structure has the following problems:

1. The two part assembly of top cap to cylindrical chamber is expensiveand prone to leak, and the residual solvent adhesive is potentiallytoxic to the blood.

2. These top caps and chambers are generally round in cross section forinjection molding and assembly reasons. Otherwise leaks will occur evenmore frequently. However, the round shape leaves barely sufficient roomfor the three to four ports which must communicate through the top capto the interior of the drip chamber. These access ports must fittypically within a 15-18 mm. O.D. (outer diameter) area of the top cap,eliminating the chance of directly connecting a pump segment to a dripchamber, which typically is a 12 mm. O.D. tube placed in a port havingan O.D. of about 14 mm. Arterial drip chambers are always in closeproximity to a pump segment but, because of the above, the drip chambermust be connected to the pump segment via a pump segment connectorattached to a length of blood tube, the end of which can fit on the topcap. This is an expensive solution, also prone to leaks and highresiduals of solvents.

3. Drip chambers are placed in arterial bloodlines either downstream ofthe pump segment ("post-pump") or upstream ("pre-pump"), depending onthe prescription of the physician and the type of dialysis machine.Pre-pump arterial chamber bloodlines are more expensive to make becausethe IV saline port must often be mounted on a separate "T" connectorupstream from the drip chamber. On "post-pump" bloodlines the IV salineport can be mounted on the inlet pump segment connector, thus saving onepart and one tube and the assembly thereof. This combination connectionalso reduces leaks and solvent residuals.

There are a number of reasons why the IV saline port location isdifferent in "pre-pump" and "post-pump" bloodlines, but each relates tothe necessity of administering saline upstream from the arterial dripchamber:

a. During the priming procedure prior to dialysis, the arterial tubingupstream from the IV saline port must be retrograde primed. A dripchamber in this segment is difficult to retrograde prime.

b. During dialysis, saline infusion (for relief of hypotension) is mostsafely done if any entrained bubbles are caught by a downstream arterialdrip chamber. Also, the saline flow can only be visualized if there is adrip chamber downstream.

c. During rinse-back of blood to the patient at the end of dialysis, thearterial fistula and the arterial blood tube upstream from the IV salineport must be retrograde flushed with saline to return this blood to thepatient. To counteract the resistance of blood pressure, the saline bagis typically squeezed to create retrograde saline flow. This resistanceis much greater if a drip chamber is upstream from the IV saline port.(Note: rinse-back of the downstream portion of the arterial and venouslines is done by the blood pump so resistance in this direction isunimportant). Further, retrograde rinse of blood tubing is desirably of"plug flow" type, resulting in little saline being added to the patient.If a drip chamber is upstream from the IV saline port, the blood in thedrip chamber is diluted slowly by saline, resulting in large amounts ofsaline being administered to the patient. This is a problem, since oneof the goals of dialysis is to remove fluid from the patient.

One partial solution to the problems of arterial chamber has been theuse of blow-molding to make one piece chambers. Thus, the two partassembly problems discussed above are eliminated. The other problemsremain.

Also, the blowmolded chambers in the literature are all so-called"bottom entry" chambers whereby the blood inlet port is at the bottom ofthe chamber and blood enters into the blood space at the bottom orsidewall of the chamber. (This is opposite to "top entry" chambers, allinjection molded so far, where blood enters at or adjacent the top intothe airspace above the blood.) Two problems of the bottom entry chambersas disclosed in Swan U.S. Pat. No. 4,681,606, Heath U.S. Pat. No.4,668,598 and European Patent Application No. 0058325A1 are:

the inlet port enters the blood space at a point higher than the outletport, and

there is a diversion means to prevent inlet flow from breaking thesurface of the blood space and causing foaming, such diversion directingthe flow in the direction of the blood outlet.

The first problem is that blood must often be "rinsed-back" to thepatient (at the end of dialysis) in a retrograde direction from thedialysis flow. With the inlet higher than the outlet, some blood will becaught in the chamber that cannot be returned to the chamber (the amountdetermined by the volume contained between the inlet and outlet).

The second problem is that any entrained air in the inlet blood streamis directed toward the outlet, which under certain circumstances ortoday's higher blood flows can escape. As the primary function of thechamber is as an air trap, this is a significant problem.

DESCRIPTION OF THE INVENTION

It is an object of this invention to create a one-piece, plastic, blowmolded arterial or arterial-venous blood chamber, eliminating theproblems of two-piece construction. It is another object of thisinvention to use typically blow molding to create an outboard bloodinlet port preferably capable of being connected directly to a pumpsegment tube, thus eliminating the above-discussed problems ofadditional parts and tubes. It is a third object of this invention(independent of the second object) to use blow molding to provide an IVsaline port integral with the blood inlet of the chamber, thuseliminating the problems of a separate IV saline "T" connectorconstruction as discussed above. As another independent object, aplastic blood chamber may be provided in which the blood flow can be runin either direction, for greater usefulness.

It is a fifth object to make an inlet diverter that directs blood flowand entrained air away from the blood outlet, plus a chamber with equalheight inlet and outlet for reversible flow efficiency.

The chamber may be used in a pre-pump mode. In other embodiments, thissame chamber can be connected in a post-pump mode, thereby reversing theflow direction and changing the pre-pump mode integral IV saline portinto an integral heparin port.

The blood pump operates in the same direction for both manufacturedblood lines in the pre-pump mode and the post-pump mode. In the pre-pumpmode the blood air trap chamber of this invention is undersubatmospheric or negative pressure because the blood chamber is betweenthe blood pump and the arterial fistula needle, which latter needle isthe point of major flow resistance. In the post-pump mode the chamber ofthis invention is under superatmospheric or positive pressure since thechamber is between the pump and the venous fistula needle, which isanother major point of flow resistance.

Physicians are sometimes worried about stressing a patient's fistula.Thus they like to use pre-pump designs because the negative pressure inthe pre-pump tubing segments can be monitored, giving the doctor an ideaof how much the patient's fistula is in danger of collapse.

In other situations, doctors worry more that the dialyzer will clot up,so they prefer to use post-pump designs because the positive pressure inthe post-pump tubing segments can be monitored, giving the doctor anindication that the resistance in the dialyzer is increasing.

The blood chamber of this invention may be used particularly forhemodialysis sets. The chamber comprises a sealed, round or flattenedplastic tube which defines a reservoir chamber and at least one conduitcommunicating with a first end of the reservoir chamber through a firstport, for connection with blood flow tubing of a hemodialysis set. Aconduit extends laterally along substantially the length of thereservoir chamber in spaced relation thereto, for connection withanother blood flow tubing of a hemodialysis set adjacent the reservoirchamber end which is opposed to the first end.

The blood chamber also defines a second port communicating with thereservoir chamber at the same end thereof as the first port. This secondport may also connect with blood flow tubing of the set, so that in thepre-pump mode the blood flow can pass from the second port, through theblood chamber, and to and through the first port as it passes throughthe set.

The flattened plastic tube described above also preferably defines asecond conduit extending laterally along the reservoir chamber in spacedrelation to it. The second conduit communicates with the reservoirchamber through one of the blood inlet and blood outlet ports.Typically, the second conduit may be for the administration of salinesolution, or the like, in the pre-pump mode or heparin in the post pumpmode or the like. The blood chamber of this invention may preferablydefine at least four or more separate conduits which are communicatingdirectly with the reservoir chamber.

It is preferred for the one conduit described above to connect directlywith roller pump tubing for blood flow, with this connection beingpositioned adjacent the opposed reservoir chamber end. The one conduitmay be of any desired transverse dimension adjacent the opposedreservoir chamber to accommodate the connection with the roller pumptubing in a manner that does not crowd out the desired or necessaryother ports and apertures into the blood chamber.

It is also preferred, in accordance with this invention, for the firstand second ports of the reservoir chamber to terminate inwardly atsubstantially identical longitudinal positions in the blood chamber. Inother words, they occupy an "equal height" in the blood chamber,contrary from the current configuration in an arterial chamber for adialysis set, where the blood inlet to the blood chamber is usuallyhigher than the outlet. By the arrangement of this invention, it becomespractical to run the blood reversely through the arterial chamber, whenand as that is desired, with effective operation and flow of bloodtherethrough, and without loss of a significant amount of blood withinthe arterial chamber. Thus, more blood can be returned to the patient inthe back flush step of dialysis with reverse flow through the arterialchamber of this invention.

In one preferred embodiment especially in the pre-pump mode the inlet ispositioned to divert blood flow away from the outlet.

In another preferred embodiment, the second port of the blood chambercommunicates with a second conduit extending laterally alongsubstantially the length of the reservoir chamber in spaced relationthereto. Preferably, the reservoir chamber, the one conduit, and thesecond conduit are all defined by a single, integral plastic parison,being formed typically by a known blow molding process.

Also, it may be preferred for the integral parison to also define athird conduit which communicates with the second port, and which extendslaterally along substantially the length of the reservoir chamber. Thesecond and third conduits may be used respectively for blood flow andfor the addition of saline, heparin, or other desired materials to thesystem.

The chamber may define a plurality of first access ports adjacent to afirst chamber end, one of which is a blood pump segment access port(inlet or outlet) capable of mating with a blood pump tube of typically9.0 to 14 mm. OD. This blood pump segment port can lead into the maincavity of the chamber at its bottom, side or top. Another first accessport or ports may be for pressure measurement, sample withdrawal ormedication administration.

A second blood access port may be provided at a second, opposed end ofthe chamber, and is typically capable of mating with a plastic bloodtube of typically 5.0 to 8.5 mm. OD. This second blood access port canalso lead into the body of the chamber at the bottom, side or top. Flowin this chamber may be from blood tube to pump segment or vice versa(i.e. pre-pump or post-pump). In one embodiment, the chamber defines aplurality of first access ports adjacent to a first chamber end, none ofwhich are blood pump segment or blood tubing ports. This is, they areonly ports for pressure measurement, sample withdrawal or medicationadministration. At a second, opposed end of the chamber a plurality ofports are defined, one of which is a blood pump segment access portcapable of mating with a plastic tube of typically 9.0 to 14 mm. O.D.The other access port is capable of mating with a plastic blood tube oftypically 5.0 to 8.5 mm. O.D. Both blood access ports can enter the maincavity of the chamber at the bottom, side or top.

In another embodiment, the chamber defines a plurality of first accessports adjacent to a first chamber end, two of which are blood accessports for blood tubing and a blood pump segment. At a second, opposedend of the chamber there are no ports.

An additional access port may extend from either the first end or thesecond end, but it preferably enters into the cavity of the chamber justabove the blood tube port. This serves for the administration of IVsaline in a "pre-pump" drip chamber or for administration of heparin oranticoagulant in a "post-pump" drip chamber.

The plastic arterial chambers of this invention may then be assembledinto an arterial set for hemodialysis, or may be co-blow molded with avenous chamber to form a "cassette" that may be assembled into anarterial/venous set for hemodialysis.

A fluid flow chamber cassette is described by Heath et al. U.S. Pat. No.4,666,598. The following is an improvement on that invention.

In another aspect of our invention, a blowmolded chamber cassetteresults in fewer leaks, smoother blood pathways and lower manufacturingcost than the injection molded, front-to-back assembly of the Heathdevice.

Yet another aspect is the chamber design wherein all tubing ports aresubstantially in-line with the long axis of the cassette chambers. Heathdescribes a cassette wherein transverse tubing ports must be employed,giving expense of construction as well as rough handling of the blood asit transits from axial direction to transverse direction.

Another aspect following on axial tubing port construction is a uniqueblood pump orientation. Traditional peristaltic blood pumps are in theform of an upside-down U. This relates to the design of currentlyavailable blood chambers. Heath describes a bloodpump in the form of abackwards C, offering some benefits, but at the expense of complicatedproduction method. We describe a blood pump in the form of an U, whichhas many benefits:

a. Unlike Heath, only one end of the pump segment need be tethered tothe cassette, again reducing cost of construction. The pump segment isformed straight, and is curved by the curve of the stator of the pumphousing. Heath, on the other hand, is curved into a backwards C by thepresence on the cassette of two transverse mounted pump segmentconnectors. This complicates the molding and assembly methods required.

b. Unlike upside-down U pumps, the described U pump segment primeseasily. Pump segments able to provide high bloodflow rates have largeinner diameters, in the range of 8 mm or more. In order not to crushdelicate blood cells, peristaltic pump rollers are calibrated to leave asmall gap between the pump segment walls when being crushed by therollers. This gap, however, leaks air quite readily making it difficultfor enough vacuum to be created to lift the initial column of saline upto prime the pump segment. With a U pump segment, gravity causes thesaline to fall into the pump segment, thereby priming it.

c. A U blood pump easily allows bottom-entry, bottom exit arterialchamber, which is well known to handle rapid bloodflows with lessturbulence and foaming than top-entry chambers.

DESCRIPTION OF THE DRAWINGS

Referring to the drawings, FIGS. 1a and 1b are plan views of an arterialset using the blood chamber of this invention, respectively in thepre-pump and postpump modes, ready for connection with a conventionaldialyzer and venous set;

FIG. 2 is an elevational view of the blood chamber of this invention asused in FIG. 1a, but in reversed position;

FIG. 3 is an elevational view of the blood chamber of FIG. 2 rotated 90°about its longitudinal axis;

FIG. 4 is a top plan view of the blood chamber of FIG. 2;

FIG. 5 is an elevational view of another embodiment of blood chamber ofthis invention;

FIG. 6 is a top plan view of the blood chamber of FIG. 5;

FIG. 7 is an elevational view of the blood chamber of FIG. 5, rotated90° about the longitudinal axis thereof;

FIG. 8 is an elevational view of another design of blood chamber inaccordance with this invention;

FIG. 9 is an elevational view of a double blood chamber, made from asingle flattened, plastic tube, to provide, for example, both thearterial and the venous blood chambers for a dialysis procedure in asingle unit;

FIG. 10 is an elevational view of the blood chamber assembly of FIG. 9,rotated 90° about the longitudinal axis thereof;

FIG. 11 is a top plan view of the blood chamber of FIG. 9.

FIG. 12 is a partially schematic, fragmentary view of a dialysis set upshowing a blowmolded, multiple chamber cassette similar to that shown inFIGS. 9-11 mounted on a dialysis machine; and

FIG. 13 is a top view of the cassette of FIG. 12.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to FIG. 1a, an arterial pre-pump set 10 for hemodialysis isshown, along with a conventional hollow fiber dialyzer 12 and aconventional venous set 14, with the various parts being shown ready forassembly with each other in conventional manner. Apart from the noveldisclosures herein, arterial set 10 is also shown of conventionaldesign.

A luer lock patient arterial fistula needle connector 16 is provided onone end of set 10 as shown, with the set tubing 18 extending through anon-off clamp 20, and injection site 22, extending to connect with inletport 29 of blood chamber 28 of this invention.

Roller pump segment 26 is shown to directly connect with blood outletport 27 of blood chamber 28, and extends to a pump segment connector 48,and then to tube 30 extending to connector 32 for dialyzer 12. A heparinline 24 also connects to connector 48.

Venous set 14 has similar components as shown, which are of conventionaldesign and thus do not need to be recited.

Referring to FIG. 1b, a similar arterial post-pump set 10a is shown,being of very similar design to the pre-pump set 10 except as otherwisedescribed. A luer lock patient arterial fistula needle connector 16a, asbefore, is provided at one end of set 10a, with set tubing 18a extendingthrough on--off clamp 20a and injection site 22a, in a manner similar tothe previous set. However, in this embodiment, tubing 18a connectsdirectly with pump tubing 26a. Heparin line 24 connects at the junctionbetween tubings 18a, 26a, on the other end of pump tubing 26a because ofthe different pressure considerations in the post-pump mode. Heparinmust always be administered against a positive pressure rather than areduced pressure, to avoid the catastrophic occurrence of the heparinsyringe discharging its entire contents in a few seconds into thepatient in the event of heparin pump failure.

Pump tubing 26a communicates with blood chamber 28a at blood port 27 ofthe chamber. It can be seen that chamber 28a may be the very samechamber as chamber 28, being merely reversed and with differentconnections. This provides a significant convenience in manufacturingand inventory control since the same chamber of this invention may beused in both situations without any change of design. Then, set tubing30a communicates directly with port 29 of blood chamber 28a, terminatingin a connector 32a as in the previous embodiment.

This setup may then communicate with a dialyzer 12 and a venous set 14as in the previous embodiment.

Referring also to FIGS. 2-4, blood chamber 28 or 28a may be made,typically, through a blow molding process of a moderately stiffthermoplastic, as is known in the prior art so that there may be formedout of a single, plastic, tubular parison the following: a reservoirchamber 34, and a pair of conduits 36, 38 extending laterally alongreservoir chamber 34, being spaced from the chamber by flat-sealedportions 40 of the plastic parison. Conduit 38 directly communicateswith pump segment tube 26 through port 27, with adequate room for suchconnection being available since the various ports 27, 44, 50, 52 aredistributed in a transverse line. Conduit 38 then extends the entirelength of reservoir chamber 34 to communicate therewith at the oppositeend of chamber 34.

Conduit 36 connects in branch-connection relation 42 with blood port 29.Conduit 36 also extends the length of reservoir chamber 34, spacedtherefrom by one of the flat seals 40 to a connector 44, for connectionwith a IV saline access tube in the pre-pump mode 46 having aconventional squeeze clamp 48. In the post-pump mode the tube 46a servesas a heparin tube.

Furthermore, at the end of blood chamber 28 which is remote from bloodport 29, additional ports 50, 52 can be provided for respectiveconnection with a pressure monitor line 54 and an air adjust ormedication tube 56.

Reservoir chamber 34 is capable of flat-collapse under a predeterminedsuction pressure in the manner of prior art blood chambers for theknown, desirable purposes.

Normally, blood is pumped by a roller pump from arterial patientconnector 16 or 16a into reservoir chamber 34. From there, the bloodflows out of the reservoir chamber, to pass through the remainder of thedialysis setup as shown in FIG. 1.

By this invention the first and second ports have inner ends 58, 60separated by partition 61 which occupy substantially identicallongitudinal positions along the blood chamber as particularly shown inFIG. 2, contrary to the prior art, where generally reservoir chambershave inlet ports that terminate deeper or higher within the reservoirchamber than the outlet port. It can be seen that in the pre-pump modeof FIG. 1a inner end 60 serves as the inlet to the reservoir, and thatthe inlet is constructed to cause the inlet stream of blood to bedirected laterally away from the outlet 58 by means of a curvature inpartition 61. The effect of this is to keep entrained air in the bloodaway from the outlet until the air bubbles have had a chance to rise tothe top of the blood level and join an air bubble 63 typically foundthere.

Also because of this modification, it becomes possible to effectivelyand completely run blood in reverse through the system, by reversal ofthe roller pump that operates on pump tubing 26, so that blood can bereturned to the patient through the arterial side as saline is added tothe system, for example through tube 46 or 46a. Thus, at least some ofthe blood can flow back to the patient through connector 16 or 16a in amanner that is called "plug flow", by which it is meant that the blooddoes not mix to a large degree with the saline solution which is beingused to replace it, so that the patient receives little more fluid thanthat which is found in his own blood, as the blood is returned to him orher from the dialysis set at the end of dialysis. This providessignificant advantage to the dialysis procedure and the effective returnof a maximum amount of blood to the patient after the dialysis procedurewith a minimum of saline solution.

Referring to FIGS. 5 through 7, another embodiment of blood chamber fora dialysis set is disclosed. Blood chamber 64 may be made by blowmolding as before, from a single, tubular parison to define a reservoirchamber 66 having a pair of bottom ports 68, 70. Bottom port 68 maydirectly communicate with pump tubing 26a in a manner similar to thecommunication with pump tubing 26 in the previous embodiment, pre-pumpmode, to provide blood flow out of chamber 66. Inlet flow of bloodpasses through port 70 and blood conduit 30a in a manner analogous tothe prior embodiment. This chamber may also be used in post-pump mode.

At the opposite end of blood chamber 64, a port 54a may be provided forthe pressure monitor, while another port 56a may be provided for airadjustment or the administration of medication.

An integral access tube 36a is also provided, being formed from theoriginal, blow molded parison and integral with reservoir chamber 66through a spaced, flattened, solid portion 40a of the original parison.Conduit 36a communicates at one end with an IV or saline tube 46a as inthe previous embodiment, in pre-pump mode, extending laterally along thelength of reservoir chamber 66 to join with port tube 70 so as to be incommunication with reservoir chamber 66. In post-pump mode, conduit 36aconnects to a heparin line.

As before, an arterial hemodialysis set having a blood chamber of such adesign is capable of backflushing of blood in chamber 66 and upstreamtherefrom back into the artery of the patient in a flow pattern which isreverse from the normal flow pattern, with good "plug flow" and theother advantages of such an arrangement. Also partition 61a is curved tofacilitate bubble separation as described above.

Since the end of blood chamber 64 that carries ports 68, 70 has only twoports, it is possible to use a port 68 which has adequate size todirectly receive pump segment 26a, for the advantageous elimination ofan intermediate part and to reduce the number of solvent-sealedconnections.

Referring to FIG. 8, another embodiment of this invention is shown,comprising a blood chamber 74 which, as before, is made out of a single,tubular plastic parison by blow molding.

Blood chamber 76 is shown, having an upper end with a single port 78,which may be used for connection with a pressure monitor, for example. Afirst, connected conduit 80 is shown having a connection 82 with pumptubing 26b in a manner similar to the previous embodiments. Firstconduit 80 then extends the entire length of reservoir chamber 76,making a U-turn 84 at the other end thereof into an open aperturecommunicating with reservoir chamber 76.

A second, connected inlet conduit 86 is also provided on the other sideof reservoir chamber 76, communicating at its upper end with bloodtubing 30b in a manner similar to the previous embodiments throughconnector 88. Second, connected conduit 86 then extends the length ofreservoir chamber 76, being integrally formed therewith through plasticweb 87, down to another U-turn 90, which communicates with the interiorof blood chamber 76 as does first connected conduit 80.

Thus, in the pre-pump mode blood is pumped through a set by means of apump acting on pump tubing 26b, which is directly connected to secondconduit 80. The blood passes through first conduit 86, and then entersreservoir chamber 76. The blood exits reservoir chamber 76 throughsecond conduit 80, to travel on through the dialysis setup via bloodtube 30b.

Additionally, a third connected tube 92 is formed out of the sameparison by blow molding, to be integrally connected to the remainder ofthe blood chamber by plastic web 94, which like web 87, is a part of theparison. Connected tube 92 may be, in turn, connected to saline tubing46b, with third conduit 92 extending the length of reservoir chamber 76,and joining with second, connected conduit 86 at a junction point 98,which is typically near curved portion 90. Thus, as before, blood canflow normally into reservoir chamber 76 through first connected conduit80 and out of the chamber through second connected conduit 86.

Obvious modifications may be made for post-pump use. For reverse flowthrough reservoir chamber 76, in a manner similar to the embodiment ofFIG. 2, the inlet ports 100, 102 of the respective conduits 86, 80terminate inwardly as shown at substantially identical longitudinalpositions in the blood chamber 76, to permit easy reverse flow throughthe chamber. This provides advantages as previously discussed.

Turning to FIGS. 9 through 11, in this embodiment, a single, blow-moldedparison may form blood pre-pump arterial chamber 104 and venous chamber106, for use in a combined arterial-venous hemodialysis set. Each ofblood chambers 104, 106 defines a respective conduit 108,110 whichcommunicates with a first end 112,114 of the reservoir chamber through arespective first port 116, 118.

In each case, the respective conduits 108, 110 are separated byflattened portions 120 of the parison from their respective chambers104, 106 and each other, with the conduits extending laterally alongsubstantially the length of each reservoir chamber 104, 106 in spacedrelation thereto, in accordance with this invention.

Thus, a unitary, double chamber is provided for equipping a dialysis setwith pre-pump and post-pump blood chambers, for example, or for anyother desired use.

Port 116 may be used for saline infusion when chamber 104 is undernegative pressure and for heparin infusion if it is under positivepressure as in the post-pump mode. Port 128 may be in connection to thepump tubing, while port 130 comprises the arterial blood inlet. Ports122, 124 and 126 connect to pressure monitors or serve as medicationapplication ports. Port 118 connects from the venous connector of thedialyzer, while port 132 connects to the venous patient connector.However, the multiple chamber cassette of this invention may beconnected in other ways as desired.

Referring to FIGS. 12 and 13, the cassette shown is made of a singleblowmolded parison to define a pair of chambers 204, 206, similar invirtually all respects to the cassette of FIGS. 9 through 11, and likereference numerals in the two hundreds corresponding to the samereference numerals in the one hundreds of the cassette of FIGS. 9through 11.

It can be seen that all tubing ports are substantially parallel with thelong axis of cassette chambers 204, 206. This provides an improvement ofeasier handling of the blood over, for example, transverse entry ports.

Connected to inlet 228 is pump tubing 252, which is shown to be mountedin a roller pump housing 254 so that pump tubing 252 is maintained in aU-shaped configuration which is right-side up rather than upside down oron its side, as shown. The track of housing 254 defines the shape of thepump tubing 252. The roller pump with its arms 256 and rollers 258functions in the known and normal manner to pump blood so that bloodenters the system in one specific mode from the patient artery throughinlet port 230 into chamber 204, and out of chamber 204 through port 228into pump tubing 252. Then, the blood is pumped through tubing 260 to adialyzer.

The blood from the dialyzer then enters tubing 62 to pass through port218 and separate conduit 210 to extend the length of venous chamber 206;to effect a U-turn 264, and to enter the venous chamber. Then, the bloodpasses through filter 250, through outlet port 232 and tubing 266 topass back to the patient's venous system, while moving across ultrasonic air detector 268, and link clamp 270, both of conventional design.

By this embodiment, only one end of the pump segment 252 needs to betethered to a cassette. This greatly reduces the cost of construction.The pump segment 252 may be formed straight, with the curvature beingprovided by the curve of the stator or track 254 of the pump housing.

Likewise, because the pump tubing 252 is formed in a right-side-up Usegment, as described above, high blood flow rate tubing in the range of8 mm. inner diameter or more may be readily primed, since the segmentreadily fills with liquid and stays filled.

Also, such a blood pump allows the use of bottom entry, bottom exitarterial chamber 204, which is well known to handle rapid blood flowswith less turbulence and foaming than top entry chambers.

This invention may be used as desired with single, separate chambers ofany design, or with single, blowmolded chambers, or with a multipleblowmolded cassette chamber as shown.

The above has been offered for illustrative purposes only and is notintended to limit the scope of the invention of this application, whichis as defined in the claims below.

That which is claimed:
 1. A blood chamber which comprises a sealed,integral, flattened plastic tube which defines a pair of spacedreservoir chambers, and a first conduit for each of said chambersrespectively communicating with a first end of each reservoir chamberthrough a first port, each of said first conduits extending laterallyalong substantially the length of each said reservoir chamber in spacedrelation thereto, for connection with tubing adjacent each reservoirchamber end opposed to the first end of said reservoir chamber, saidsealed, flattened plastic tube also defining a pair of second ports,each second port respectively communicating with one of the reservoirchambers.
 2. The blood chamber of claim 1 in which said reservoirchamber and said first conduits are defined by a single, integral,flattened plastic parison.
 3. The blood chamber of claim 1 in which saidspaced reservoir chambers are free of any interconnecting flow conduitswithin said flattened plastic tube.
 4. The blood chamber of claim 1 inwhich one of said reservoir chambers defines a blood inlet port and ablood outlet port positioned at the same end of said reservoir chamber.5. The blood chamber of claim 4 in which said first and second ports areseparated by a central partition, said partition defining a lateralangle to cause inflow of one of said ports to be directed laterally awayfrom the other said ports, whereby air bubbles entering through the oneof said ports are less likely to be immediately caught and sucked out ofthe chamber through the other of said ports.
 6. The blood chamber ofclaim 4 in which the other of said spaced reservoir chambers has a bloodinlet port and a blood outlet port positioned at opposite ends of saidflattened plastic tube.
 7. The blood chamber of claim 1 in which one ofsaid chambers defines an outlet port which is blocked by a filter. 8.The blood chamber of claim 1 in which one of the said chambers has aport which is directly connected with roller pump tubing, said rollerpump tubing comprising collapsible, flexible tubing which is normallystraight in unstressed configuration, and which has a free end notconnected to said flattened plastic tube.
 9. The blood chamber of claim8 in which said roller pump tubing is mounted in upright U-shape in aroller pump track.
 10. The blood chamber of claim 1 in which the firstconduit of one of said chambers is part of the blood flow path throughthe chamber, while the other first conduit of the other chambercommunicates in branched relation with the blood flow path through saidother chamber, for connection to a source of non-blood intravenoussolution.
 11. A blow molded blood chamber for hemodialysis sets whichcomprises a sealed, integral, flattened plastic tube which defines apair of spaced reservoir chambers, and a first conduit for each of saidchambers respectively communicating with the first end of each reservoirchamber through a first port, each of said first conduits extendinglaterally along substantially the length of each said reservoir chamberin spaced relationship thereto, for connection with tubing adjacent eachreservoir chamber end opposed to the first end of said reservoirchamber, said sealed, flattened plastic tube also defining a pair ofsecond ports, each second port respectively communicating with one ofthe reservoir chambers, said spaced reservoir chambers being free of anyinterconnecting flow conduits within said flattened plastic tube, one ofsaid chambers having a port which is directly connected with roller pumptubing, said roller pump tubing comprising collapsible, flexible tubingwhich is normally straight in unstressed configuration, and which has afree end not connected to said flattened plastic tube.
 12. The bloodchamber of claim 11 in which said roller pump tubing is mounted inupright U-shape in a roller pump track.
 13. The blood chamber of claim12 in which one of said reservoir chambers defines a blood inlet portand a blood outlet port positioned at the same end of said reservoirchamber.
 14. The blood chamber of claim 13 in which the other of saidspaced blood chambers has a blood inlet port and a blood outlet portpositioned at opposite ends of said flattened plastic tube.
 15. Theblood chamber of claim 14 in which the first conduit of one of saidchambers is part of the blood flow path through the chamber, while thefirst conduit of the other chamber communicates in branched relationwith the blood flow path through said other chamber, for connection to asource of non-blood intravenous solution.
 16. The blood chamber of claim15 in which one of said chambers defines an outlet port which is blockedby a filter.
 17. A blood chamber which comprises a sealed, plastic tubewhich defines a reservoir chamber and a pair of conduits communicatingwith a first end of said reservoir chamber through first and secondports, said first and second ports being separated by a centralpartition, said partition defining a lateral angle to cause inflow fromone of said ports to be directed laterally away from the other of saidports, whereby air bubbles entering through the one of said ports areless likely to be immediately caught and sucked out of the chamberthrough the other of said ports.
 18. The blood chamber of claim 17 inwhich said chamber has a port which is directly connected with rollerpump tubing, said roller pump tubing comprising collapsible, flexibletubing which has a free end not connected to said flattened plastictube.